The present invention relates to floor grids having spaced rails for use in entrances of buildings to facilitate removal of debris such as dirt, snow, water, etc., from traffic passing thereover.
Conventional structures for removal of debris from shoes of pedestrians have been unsatisfactory in that one or more of the tread supporting members tends to work loose and becomes dangerous, especially where vehicles which vibrate and shock the grid use the same trafficway. In particular, some of the conventional structures utilize a long key or slide bar which secures together and properly spaces all of the tread supporting members. These keys or slide bars have a tendency to work loose with vibration or wear and to, thus, loosen all of the tread supporting members along the key or bar. The tread supporting members are thereafter wobbly and easily turned which contributes to tripping and falls by the pedestrians and also tends to leave too wide a gap therebetween thus catching the heels of the pedestrians' shoes.
Another prior art structure includes tread support members which have a downwardly opening channel with grooved sides. Threaded bolts anchored in the support structure of the structure engage and tap the grooves. This structure also has a tendency to loosen with time and become dangerous, especially since the bolts are not captured by a complete thread extending entirely around the bolt.
The prior art devices also normally require complete disassembly of the tread support members from the supporting strucure in order to remove any one support member and thus fail to provide for easy removal and replacement of such a support member which is damaged. It is also often difficult to clean beneath conventional devices to remove accumulated debris.